Estimation of Hydraulic Conductivity and Retention of Soil with High gravel content ,A Case Study.

• Main Authors: Jean,Jin-Long, 簡金龍
• Other Authors: Lee,Tim-Hau
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/93506083937409743959

碩士 === 國立臺灣大學 === 土木工程研究所 === 84 === The purpose of this study is to investigate how the unsaturated flow in vadose zone is affected by gravels in soil. A model k and Watson (Dunn and Mehuys, 1984) to estimate saturated conductivity by the volume ratio of gravel content was verified sand-box (1m*1m*2m) experiment. Wetting process and drying experiments were conducted with the sand box. Simulation result Finite-Analytic Model for unsaturated porous media flow was to the measurements of tensiometers, which were buried at depths in the sand box. Physical and hydraulic properties of the background soil, such as particle density, particle size soil moisture retention curve,unsaturated hydraulic conductivity were analyzed.Compared to the saturated hydraulic conductivity at the sand box , it was discovered the estimate by Peck and Watson''s Model was poor for the reasons of high gravel content irregular gravel shape of the sample. When the model estimate was corrected by the gravel''s shape factor proposed by this study, a reasonably accurate estimate was achieved. The soil retention a suction head below 100cm can not be accurately measured due to sensitivity limit of the pressure plate extractor. It has to be estimated by extrapolation with the data over 100 cm suction Haverkamp,s empirical formula is used for data fitting. For the air-entry pressure of the soil sample was quite high (about a major part of the sand box was within the capillary fringe. simulation result with the fitted retention curve as an input depict the soil moisture movement in the sand box. Parameter identification was conducted to calibrate the retention curve at suction end with tensiometer measurements during wetting application of the calibrated retention curve makes the result more consistent with the measurements, either during a or a drying process.